src/probes/lttng-uprobes.c

   1 /* SPDX-License-Identifier: (GPL-2.0-only OR LGPL-2.1-only)
   2  *
   3  * probes/lttng-uprobes.c
   4  *
   5  * LTTng uprobes integration module.
   6  *
   7  * Copyright (C) 2013 Yannick Brosseau <yannick.brosseau@gmail.com>
   8  * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   9  *
  10  */
  11
  12 #include <wrapper/fdtable.h>
  13 #include <linux/list.h>
  14 #include <linux/module.h>
  15 #include <linux/namei.h>
  16 #include <linux/slab.h>
  17 #include <linux/uaccess.h>
  18 #include <linux/uprobes.h>
  19
  20 #include <lttng/events.h>
  21 #include <lttng/events-internal.h>
  22 #include <lttng/tracer.h>
  23 #include <wrapper/irqflags.h>
  24 #include <ringbuffer/frontend_types.h>
  25 #include <wrapper/vmalloc.h>
  26
  27 static
  28 int lttng_uprobes_event_handler_pre(struct uprobe_consumer *uc, struct pt_regs *regs)
  29 {
  30         struct lttng_uprobe_handler *uprobe_handler =
  31                 container_of(uc, struct lttng_uprobe_handler, up_consumer);
  32         struct lttng_kernel_event_common *event = uprobe_handler->event;
  33         struct lttng_kernel_probe_ctx lttng_probe_ctx = {
  34                 .event = event,
  35                 .interruptible = !lttng_regs_irqs_disabled(regs),
  36         };
  37         struct {
  38                 unsigned long ip;
  39         } payload;
  40
  41         switch (event->type) {
  42         case LTTNG_KERNEL_EVENT_TYPE_RECORDER:
  43         {
  44                 struct lttng_kernel_event_recorder *event_recorder =
  45                         container_of(event, struct lttng_kernel_event_recorder, parent);
  46                 struct lttng_kernel_channel_buffer *chan = event_recorder->chan;
  47
  48                 if (unlikely(!LTTNG_READ_ONCE(chan->parent.session->active)))
  49                         return 0;
  50                 if (unlikely(!LTTNG_READ_ONCE(chan->parent.enabled)))
  51                         return 0;
  52                 break;
  53         }
  54         case LTTNG_KERNEL_EVENT_TYPE_NOTIFIER:
  55                 break;
  56         default:
  57                 WARN_ON_ONCE(1);
  58         }
  59
  60         if (unlikely(!LTTNG_READ_ONCE(event->enabled)))
  61                 return 0;
  62
  63         switch (event->type) {
  64         case LTTNG_KERNEL_EVENT_TYPE_RECORDER:
  65         {
  66                 struct lttng_kernel_event_recorder *event_recorder =
  67                         container_of(event, struct lttng_kernel_event_recorder, parent);
  68                 struct lttng_kernel_channel_buffer *chan = event_recorder->chan;
  69                 struct lttng_kernel_ring_buffer_ctx ctx;
  70                 int ret;
  71
  72                 lib_ring_buffer_ctx_init(&ctx, event_recorder,
  73                         sizeof(payload), lttng_alignof(payload), &lttng_probe_ctx);
  74
  75                 ret = chan->ops->event_reserve(&ctx);
  76                 if (ret < 0)
  77                         return 0;
  78
  79                 /* Event payload. */
  80                 payload.ip = (unsigned long)instruction_pointer(regs);
  81
  82                 chan->ops->event_write(&ctx, &payload, sizeof(payload), lttng_alignof(payload));
  83                 chan->ops->event_commit(&ctx);
  84                 break;
  85         }
  86         case LTTNG_KERNEL_EVENT_TYPE_NOTIFIER:
  87         {
  88                 struct lttng_kernel_event_notifier *event_notifier =
  89                         container_of(event, struct lttng_kernel_event_notifier, parent);
  90                 struct lttng_kernel_notification_ctx notif_ctx;
  91
  92                 notif_ctx.eval_capture = LTTNG_READ_ONCE(event_notifier->eval_capture);
  93                 event_notifier->notification_send(event_notifier, NULL, NULL, &notif_ctx);
  94                 break;
  95         }
  96         default:
  97                 WARN_ON_ONCE(1);
  98         }
  99         return 0;
 100 }
 101
 102 static const struct lttng_kernel_event_field *event_fields[] = {
 103         lttng_kernel_static_event_field("ip",
 104                 lttng_kernel_static_type_integer_from_type(unsigned long, __BYTE_ORDER, 16),
 105                 false, false),
 106 };
 107
 108 static const struct lttng_kernel_tracepoint_class tp_class = {
 109         .nr_fields = ARRAY_SIZE(event_fields),
 110         .fields = event_fields,
 111 };
 112
 113 /*
 114  * Create event description.
 115  */
 116 static
 117 int lttng_create_uprobe_event(const char *name, struct lttng_kernel_event_common *event)
 118 {
 119         struct lttng_kernel_event_desc *desc;
 120         int ret;
 121
 122         desc = kzalloc(sizeof(*desc), GFP_KERNEL);
 123         if (!desc)
 124                 return -ENOMEM;
 125         desc->tp_class = &tp_class;
 126         desc->event_name = kstrdup(name, GFP_KERNEL);
 127         if (!desc->event_name) {
 128                 ret = -ENOMEM;
 129                 goto error_str;
 130         }
 131         desc->owner = THIS_MODULE;
 132         event->priv->desc = desc;
 133
 134         return 0;
 135
 136 error_str:
 137         kfree(desc);
 138         return ret;
 139 }
 140
 141 /*
 142  * Returns the inode struct from the current task and an fd. The inode is
 143  * grabbed by this function and must be put once we are done with it using
 144  * iput().
 145  */
 146 static struct inode *get_inode_from_fd(int fd)
 147 {
 148         struct file *file;
 149         struct inode *inode;
 150
 151         rcu_read_lock();
 152         /*
 153          * Returns the file backing the given fd. Needs to be done inside an RCU
 154          * critical section.
 155          */
 156         file = lttng_lookup_fd_rcu(fd);
 157         if (file == NULL) {
 158                 printk(KERN_WARNING "LTTng: Cannot access file backing the fd(%d)\n", fd);
 159                 inode = NULL;
 160                 goto error;
 161         }
 162
 163         /* Grab a reference on the inode. */
 164         inode = igrab(file->f_path.dentry->d_inode);
 165         if (inode == NULL)
 166                 printk(KERN_WARNING "LTTng: Cannot grab a reference on the inode.\n");
 167 error:
 168         rcu_read_unlock();
 169         return inode;
 170 }
 171
 172
 173 static
 174 int lttng_uprobes_add_callsite(struct lttng_uprobe *uprobe,
 175         struct lttng_kernel_abi_event_callsite __user *callsite,
 176         int (*handler)(struct uprobe_consumer *self, struct pt_regs *regs),
 177         void *priv_data)
 178 {
 179         int ret = 0;
 180         struct lttng_uprobe_handler *uprobe_handler;
 181
 182         if (!priv_data) {
 183                 ret = -EINVAL;
 184                 goto end;
 185         }
 186
 187         uprobe_handler = kzalloc(sizeof(struct lttng_uprobe_handler), GFP_KERNEL);
 188         if (!uprobe_handler) {
 189                 printk(KERN_WARNING "LTTng: Error allocating uprobe_handler");
 190                 ret = -ENOMEM;
 191                 goto end;
 192         }
 193
 194         /* Ensure the memory we just allocated don't notify page faults. */
 195         wrapper_vmalloc_sync_mappings();
 196
 197         uprobe_handler->event = priv_data;
 198         uprobe_handler->up_consumer.handler = handler;
 199
 200         ret = copy_from_user(&uprobe_handler->offset, &callsite->u.uprobe.offset, sizeof(uint64_t));
 201         if (ret) {
 202                 goto register_error;
 203         }
 204
 205         ret = uprobe_register(uprobe->inode,
 206                       uprobe_handler->offset, &uprobe_handler->up_consumer);
 207         if (ret) {
 208                 printk(KERN_WARNING "LTTng: Error registering probe on inode %lu "
 209                        "and offset 0x%llx\n", uprobe->inode->i_ino,
 210                        uprobe_handler->offset);
 211                 ret = -1;
 212                 goto register_error;
 213         }
 214
 215         list_add(&uprobe_handler->node, &uprobe->head);
 216
 217         return ret;
 218
 219 register_error:
 220         kfree(uprobe_handler);
 221 end:
 222         return ret;
 223 }
 224
 225 int lttng_uprobes_event_add_callsite(struct lttng_kernel_event_common *event,
 226         struct lttng_kernel_abi_event_callsite __user *callsite)
 227 {
 228         return lttng_uprobes_add_callsite(&event->priv->u.uprobe, callsite,
 229                 lttng_uprobes_event_handler_pre, event);
 230 }
 231 EXPORT_SYMBOL_GPL(lttng_uprobes_event_add_callsite);
 232
 233 static
 234 int lttng_uprobes_register(struct lttng_uprobe *uprobe, int fd)
 235 {
 236         int ret = 0;
 237         struct inode *inode;
 238
 239         inode = get_inode_from_fd(fd);
 240         if (!inode) {
 241                 printk(KERN_WARNING "LTTng: Cannot get inode from fd\n");
 242                 ret = -EBADF;
 243                 goto inode_error;
 244         }
 245         uprobe->inode = inode;
 246         INIT_LIST_HEAD(&uprobe->head);
 247
 248 inode_error:
 249         return ret;
 250 }
 251
 252 int lttng_uprobes_register_event(const char *name, int fd, struct lttng_kernel_event_common *event)
 253 {
 254         int ret = 0;
 255
 256         ret = lttng_create_uprobe_event(name, event);
 257         if (ret)
 258                 goto error;
 259
 260         ret = lttng_uprobes_register(&event->priv->u.uprobe, fd);
 261         if (ret)
 262                 goto register_error;
 263
 264         return 0;
 265
 266 register_error:
 267         kfree(event->priv->desc->event_name);
 268         kfree(event->priv->desc);
 269 error:
 270         return ret;
 271 }
 272 EXPORT_SYMBOL_GPL(lttng_uprobes_register_event);
 273
 274 static
 275 void lttng_uprobes_unregister(struct inode *inode, struct list_head *head)
 276 {
 277         struct lttng_uprobe_handler *iter, *tmp;
 278
 279         /*
 280          * Iterate over the list of handler, remove each handler from the list
 281          * and free the struct.
 282          */
 283         list_for_each_entry_safe(iter, tmp, head, node) {
 284                 uprobe_unregister(inode, iter->offset, &iter->up_consumer);
 285                 list_del(&iter->node);
 286                 kfree(iter);
 287         }
 288 }
 289
 290 void lttng_uprobes_unregister_event(struct lttng_kernel_event_common *event)
 291 {
 292         lttng_uprobes_unregister(event->priv->u.uprobe.inode, &event->priv->u.uprobe.head);
 293 }
 294 EXPORT_SYMBOL_GPL(lttng_uprobes_unregister_event);
 295
 296 void lttng_uprobes_destroy_event_private(struct lttng_kernel_event_common *event)
 297 {
 298         iput(event->priv->u.uprobe.inode);
 299         kfree(event->priv->desc->event_name);
 300         kfree(event->priv->desc);
 301 }
 302 EXPORT_SYMBOL_GPL(lttng_uprobes_destroy_event_private);
 303
 304 void lttng_uprobes_destroy_event_notifier_private(struct lttng_kernel_event_notifier *event_notifier)
 305 {
 306         iput(event_notifier->priv->parent.u.uprobe.inode);
 307         kfree(event_notifier->priv->parent.desc->event_name);
 308         kfree(event_notifier->priv->parent.desc);
 309 }
 310 EXPORT_SYMBOL_GPL(lttng_uprobes_destroy_event_notifier_private);
 311
 312 MODULE_LICENSE("GPL and additional rights");
 313 MODULE_AUTHOR("Yannick Brosseau");
 314 MODULE_DESCRIPTION("Linux Trace Toolkit Uprobes Support");